Accelerators of vulcanization



Patented May 26, 1936 UNITED STATES PATENi'lT" ore-ice ACCEIz'ERATORS' OF VULCANIZATION Albert F. Hardman, Cumberland, Md., assignor,.. by mesne assignments, to The Kelly- Springfield 7 Tire Company, Cumberland; Md.,.a corporationof Maryland No Drawing, Application June 2,6;v 1933,- Serial No. 677,679

14 Claims.

The present invention relates to the art ofrub. ben. manufacture and. particularly relates. to a new. class of rubber vulcanization accelerators for use in the vulcanization of rubber and rubberlike products.

The new and preferredclass of. accelerators be represented by the structural formula XR-(%O.R!

wherein X representsone. or more dithio acid residues of the formula R representing an organic radical, R5 represents an aliphatic radical and R represents an ester forming radical. The compounds accordingto the present invention are obtainable by reacting; a salt of a dithio acidwith an ester: of a halogen substituted aliphatic acid.

As examples of the new and preferred class of accelerators: and included withinthe scope'of thepresent invention arethe-following: benzyl di thiofuroicacetate, cyclohexyl"dithiofuroicacetate;

phenyl dithiofuroicacetate; beta naphthyl dithio-- proportions of ammonium dithiofuroateand: substantially onemolecular proportion of ethyl diichl'oracetate); reaction product of' substantially one; molecular proportion of" an alkali metalisalt, for example, the potassium salt-of diethyl-dithi'ocarbamate and substantially one molecular proportion of ethyl chl'oracetate, reactioniproductt of 50 substantially one molecular proportionof an alkali metal salt, for example; the potassium salt of ethyl xanthic acid and substantially one molecular proportion-lof butylchloracetate, reaction product of substantially one molecular pro- 55 rtiomof sodiumrbutylganthate. and substantiall y, one; molecular; proportion of ethyl chlorformate and the reaction product ofisubstantially two; molecular; proportions; of. potassium amyl xanthate and substantially one molecular proportion of amyl= dichlorpropionate. hereinbeforeset forth are typical members of the new and preferred class of, rubber vulcanization accelerators.

Thefollowing are to beunderstood as i1lus-v trative: embodiments of the. invention and not limitative of the scope thereof;

Ewamplezk 2.00 grams of' ammonium dithiofuroate; containing about 1'(I-..-201%'1 of water. insoluble" impurities, were dissolved in.,6.0,0. cc. ,ofiwarnr Water-and filtered. The filtrate thus obtained'was placed in a suitable reactor equipped with an agitator and1-35g. offethyl chloracetate added. The-re.

acting: components wereagitated vigorously for substantially-five hours'at a temperature of substantially 40'-50-"- (3., duringrw-hich time cooling: was effected by surrounding thereaction 1 vessel-i with cold water. After the-reaction was com pleted, the'reaction product was poured into an equal volume" of cold'water; and the oilseparated therefrom. The separated oil was washed with waterand dried over a suitable drying agent, for example" anhydrouscalciumbhloride. A- yield of 2.41 g. of'aclear redliquid was obtained; which;

after recrystallization oncefrom" ethyl alcohol} had a melting pointof-ZB G.- I-t isbelieved the reaction.- describedrabovemay: be: represented as follows:

The. ethyl dithiofuroicacetate prepared as described was incorporatedin. the usuah manner in a rubber: stock. comprising Harts. Smoked sheet rubber 109 Sulfur 3 Zinc oxide; 53 Stearic acid 2 Accelerator 0i8,5

After vulcanizing by heating for: difierentperiods of time at the temperature of"2 0- pounds ofsteanr pressure per square inch; (258, 11), the

The. examples. 7

following tensile and modulus data were obtained.

From the data set forth in 'Ifable I it is readily apparent that the preferred class of materials, for example ethyl dithiofuroicacetate, ex-

hibits desirable qualities as vulcanization accelerators.

Furthermore, the new class of accelerators has been .foundto possess the desired delayed action; e. g., no cure is produced during the milling of the rubber stock.

Among other examples of the new class of accelerators which have been prepared in a manner analogous to that described above are:-

- Melting point Benzyl dithiofuroicacetate C. Cyclohexyl dithiofuroicacetate 58 C. ;Phenyl dithiofuroicacetate 105 C. Beta naphthyl dithiofuroicacetate 71 C. Methyl dithiofuroicacetate 16 C. Butyl dithiofuroicacetateu 9 C. Amyl dithiofuroicacetate Capryl dithiofuroicacetate 17? C. Normal propyl dithiofuroicacetate 43 C.

Iso-propyl dithiofuroicacetate;

The melting points given above for the first four compounds were obtained on once recrystallized materials. The melting points set forth for the remainder of the compounds were those obtained on the unpurified product. Further purification would probably cause slight differences in this physical property.

The products hereinafter described were compounded in the usual manner in a rubber stock comprising 7 To the base rubber stock there were added the accelerators in the quantities set forth.: After a vulcanizing by heating in a press for the periods indicated, at the temperature of 20 pounds of steam pressure per square inch (258 F.), the cured rubber product possessed the tensile and modulus characteristics given in Table II.

Table II Modulusoi g gf Cure elasticity in Tensile at Accelerator is 'mins lbs./in. at break in g, elongation of lbs./in. p 500 percent Benzyldithioturoicace- H tate l. 075 r 10 Blown Cyclohexyl dithioiuroicacetate l. 045 10 Blown Phenyldithioiuroicacetate 1. 025 10 Blown Beta naphthyl d r I furoicacetate l. 21 l0 Blown Methyl dithioiuroic- -acetate... 0.795 p 10 Blown I te 0. 10 Blown Amyl dithiofuroicacetate 1.00 10 Blown From the data set forth in Table II it has been.

shown that the compounds described when incorporated in a rubber stock are all strong vuli-- canization accelerators. Further all have been. found to possess delayed action..

Normal propyl dithiofuroicacetate and isopropyl dithiofuroicacetate have also been incorporated in rubber stocks and have been found to possess the accelerating properties typical of the.

class.

By the term alkali: metalas set forthin the claims attached hereto as a part of thepresent specification is meant the alkali metals, lithium, potassium, sodium, caesium and rubidium, together with ,thQyHQ group.

The presentinvention is not limited to the specific examples given above, as they are to be ,construed as specific embodiments of the pres- 1. A rubber vulcanization accelerator of the general structure n-k -s-lv-ce-o-n V S V V I where R represents a'furyl radical, R represents Table IICorit1nued Modulus of 3 33:? cm elastici in Tensile at Accelerator stator mins lbs./in. at breakin arts elongation of 1 lbs./ in. p 500 percent Capryl dithioiuroicacel. 25 10 Blown Benzyl dithioluroicacetate 1. 075 15 450 306% Gyclohexyl dithiofuroice. 1. 045 15 550 3980 Phenyl dithioiuroicacetate 1.025 15 450 3300 Beta naphthyl furoicacetate 1.-2L 15 550 3660 Methyl dithioiuroicacetate- 0.795 15 470 2810: Butyl dithioiuroicace- 5 Q. 95 15 420 2710 Amyl dithiofuroicacetate 1.00 15 530 3340 Capryl dithi0furoiace tate 1. 25 15 350 1. 2540 Benzyl glithioiuroicacetate 1.075 20 580 3700 Cyelohexyl dithioiuroicacetate 1. 045 20 I 750 4100- Phenyl dithioiuroicacetate 1.025 20 j 670 5840' Beta naphthyl dithiov furoicacetate 1. 21 20 700 39 10- Methyl dithiofuroicacetate. 0. 795 20 710 4060 Butyl dithioiuroicacetate 0.95 20 700 4350 tate l. 00 20 710 4320 Capryl dithioiuroicacetate 1. 25 20 Benzyldithioiul'oicacet e 1. 075 30 690 4020' Cyclohexyl dithiofuroicacetate 1. 045 30 800 4200 Phenyl dithiofuroicacetate 1.025 30 750 4200' Beta naphthyl furoicacetate. 1.21 30 740 3700 Methyl dithiofuroicacetate 0. 795 30 800 3580 Butyl dithioiuroicacetate 0. 95 30 800 4210" Amyl dithiofuroicacetate 1.00 30 770 43% Capryl dithioiuroicq acetate 1.25 30 750 4036 I an alkylene group and R. represents a hydrocarbon ester forming radical.

2. A rubber vulcanization accelerator of the general structure wherein R represents the furyl radical, R. represents the methylene group and It represents an alkyl radical.

3. A rubber vulcanization accelerator comprising ethyl dithiofuroicacetate.

4. A rubber vulcanization accelerator comprising phenyl dithiofuroicacetate.

5. A rubber vulcanization accelerator comprising cyclohexyl dithiofuroicacetate.

6. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a rubber vulcanization accelerator of the general where R represents a furyl radical, R represents an alkylene group and R represents a hydrocarbon ester forming radical.

7. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a rubber vulcanization accelerator of the general structure wherein R represents the furyl radical, R, represents the methylene group and It represents an alkyl radical.

8. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising ethyl dithiofuroicacetate.

9. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising phenyl dithiofuroicacetate.

10. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a rubber vulcanization accelerator comprising cyclohexyl dithiofuroicacetate.

11. A rubber vulcanization accelerator of the general structure where It represents a furyl radical, R represents an aliphatic hydrocarbon radical, R represents a hydrocarbon ester forming radical and n represents a whole number less than three.

12. A rubber vulcanization accelerator of the general structure XRCORI, H

where X is a dithiofuroic acid residue, R represents as aliphatic hydrocarbon radical, R represents a hydrocarbon ester forming radical.

13. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a vulcanization accelerator of the general structure where Xis a dithiofuroic acid residue, R represents an aliphatic hydrocarbon radical, R represents a hydrocarbon ester forming radical.

ALBERT F. HARDMAN. 

